Display panel

ABSTRACT

A display panel is provided. The display panel includes a display layer, a light diffusion layer, and a light guide plate. The display layer is used to display an image. The light guide plate is disposed under the display layer. The light guide plate guides a light of a back light source to the display layer. The light diffusion layer is disposed between the display layer and the light guide plate. The light diffusion layer is controlled by at least one control voltage, so as to dynamically change the transparency of the light diffusion layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan applicationserial no. 105138790, filed on Nov. 25, 2016. The entirety of theabove-mentioned patent application is hereby incorporated by referenceherein and made a part of this specification.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to an electronic device and more particularlyrelates to a display panel.

Description of Related Art

With the progress of technology, two-dimensional images displayed by thetraditional display screen can no longer satisfy people's needs. Thetraditional display screen with a back light would block the user's viewand therefore the user cannot see behind the display screen. A liquidcrystal display screen that does not use back light may allow the userto see the object behind the display screen through the display screen.Nevertheless, the images displayed by such a see-through display screenusually have poor brightness.

SUMMARY OF THE INVENTION

The invention provides a display panel which provides a back light toenhance the brightness of an image and dynamically decides whether toprovide a see-through function.

According to an embodiment of the invention, a display panel isprovided, which includes a display layer, a light guide plate, and alight diffusion layer. The display layer is used to display an image.The light guide plate is disposed under the display layer and guides alight of a back light source to the display layer. The light diffusionlayer is disposed between the display layer and the light guide plate.The light diffusion layer is controlled by at least one control voltage,so as to dynamically change a transparency of the light diffusion layeraccording to the at least one control voltage.

Based on the above, the display panel disclosed in the embodiments ofthe invention includes the transparent light guide plate and the lightdiffusion layer that dynamically changes the transparency. The lightguide plate guides the light of the back light source to pass throughthe light diffusion layer and enter the display layer in a scattered ortransmissive manner, so as to enhance the brightness of the image of thedisplay layer. When the light diffusion layer presents the transparentstate, the user is able to see the object behind the display panelthrough the display panel as well as see the image displayed by thedisplay layer. Thus, the display panel according to the embodiments ofthe invention enhances the brightness of the image with back light anddynamically decides whether to provide the see-through function.

To make the aforementioned and other features and advantages of theinvention more comprehensible, several embodiments accompanied withfigures are described in detail as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate exemplaryembodiments of the invention and, together with the description, serveto explain the principles of the invention.

FIG. 1A is a schematic cross-sectional view of the display panelaccording to an embodiment of the invention.

FIG. 1B is a schematic cross-sectional view of the light diffusion layershown in FIG. 1A according to an embodiment of the invention.

FIG. 2A is a schematic cross-sectional view of the display panelaccording to another embodiment of the invention.

FIG. 2B is a schematic cross-sectional view of the light reflectionlayer shown in FIG. 2A according to another embodiment of the invention.

FIG. 3A is a schematic cross-sectional view of the display panelaccording to yet another embodiment of the invention.

FIG. 3B is a schematic view of the image displayed by the display panelof FIG. 3A.

FIG. 4 is a schematic cross-sectional view of the display panelaccording to yet another embodiment of the invention.

FIG. 5A is a schematic layout diagram of the sub-pixel of the displaylayer and the light guide microstructure of the light guide plateaccording to an embodiment of the invention.

FIG. 5B is a schematic layout diagram of the light guide microstructureof the light guide plate according to an embodiment of the invention.

FIG. 5C is a schematic cross-sectional view of the light guidemicrostructure of the light guide plate according to an embodiment ofthe invention.

FIG. 5D is a schematic cross-sectional view of the light guidemicrostructure of the light guide plate according to another embodimentof the invention.

FIG. 6A is a schematic layout diagram of the light guide microstructureof another light guide plate.

FIG. 6B is a schematic layout diagram of the sub-pixel of the displaylayer and the light guide microstructure of the light guide plate shownin FIG. 6A according to another embodiment.

DESCRIPTION OF THE EMBODIMENTS

The term “couple (or connect)” used throughout this specification(including the claims) may refer to any direct or indirect connectionmeans. For example, if it is described that the first device is coupled(or connected) to the second device, it should be understood that thefirst device may be directly connected to the second device orindirectly connected to the second device through other devices orcertain connection means. Moreover, elements/components/steps with thesame reference numerals represent the same or similar parts in thefigures and embodiments where appropriate. Descriptions of theelements/components/steps with the same reference numerals or terms indifferent embodiments may be reference for one another.

FIG. 1A is a schematic cross-sectional view of a display panel 100according to an embodiment of the invention. According to the designrequirements, the display panel 100 may be applied to a laptop computer,a tablet computer, a handheld electronic device, a display, an automaticvending machine, or other electronic devices. The display panel 100 iscapable of dynamically determining whether to provide a see-throughfunction. When the display panel 100 provides the see-through function,the user is able to see an object behind the display panel 100 throughthe display panel 100 as well as see an image displayed by a displaylayer 110. When the display panel 100 does not provide the see-throughfunction, the user only sees the image displayed by the display panel100 and is not able to see the object behind the display panel 100through the display panel 100.

The display panel 100 includes a display layer 110, a light diffusionlayer 120, a light guide plate 130, and a back light source 140. Theback light source 140 may be a cold cathode fluorescent lamp (CCFL)light source, a light emitting diode (LED) light source, or other backlight sources. The back light source 140 is disposed on a lateral sideof the light guide plate 130. The back light source 140 may emit a lightinto the light guide plate 130. The light guide plate 130 is disposedunder the display layer 110. A material of the light guide plate 130 isa transparent material. The light guide plate 130 has a light guidestructure, such that the light guide plate 130 is able to guide thelight of the back light source 140 to the light diffusion layer 120 andthe display layer 110. The display layer 110 is for displaying an image.According to the design requirements, the display layer 110 may includea liquid crystal display panel or other types of display panels. Theliquid crystal display panel may be a twisted nematic (TN) displaypanel, a super-twisted nematic (STN) display panel, a vertical alignment(VA) display panel, an in-plane switching (IPS) display panel, a thinfilm transistor (TFT) display panel, or other conventional liquidcrystal display panels. Thus, details thereof will be omittedhereinafter. According to the design requirements, the display layer 110may simply provide a display function, or may provide both the displayfunction and a touch detection function.

The light diffusion layer 120 is disposed between the display layer 110and the light guide plate 130. The light diffusion layer 120 iscontrolled by a control voltage V1, so as to dynamically change thetransparency of the light diffusion layer 120. As an example (but notlimited thereto), when the control voltage V1 exceeds a thresholdvoltage Vt1, the light diffusion layer 120 presents a transparent state.When the control voltage V1 is lower than the threshold voltage Vt1, thelight diffusion layer 120 presents a non-transparent state (e.g., hazy).The threshold voltage Vt1 is determined by a material property of thelight diffusion layer 120. When the light diffusion layer 120 is in thetransparent state, the light guided by the light guide plate 130 passesthrough the light diffusion layer 120 and enters the display layer 110,so as to enhance the brightness of the image of the display layer 110.At this moment, the user is able to see the object behind the displaypanel 100 through the display panel 100 as well as see the imagedisplayed by the display layer 110. When the light diffusion layer 120is in the non-transparent state, the light of the back light source 140guided by the light guide plate 130 passes through the light diffusionlayer 120 and enters the display layer 110 in a scattered manner, so asto enhance the brightness of the image of the display layer 110. At thismoment, the user is able to see only the image displayed by the displaylayer 110 and cannot see the object behind the display panel 100 throughthe display panel 100.

FIG. 1B is a schematic cross-sectional view of the light diffusion layer120 shown in FIG. 1A according to an embodiment of the invention. In theembodiment shown in FIG. 1B, the light diffusion layer 120 includes afirst electrode 121, a polymer dispersed liquid crystal (PDLC) 122, anda second electrode 123. The polymer dispersed liquid crystal 122 mayrelatively change/present different transparencies according todifferent electric field intensities. The polymer dispersed liquidcrystal 122 is disposed between the first electrode 121 and the secondelectrode 123. A material of the first electrode 121 and the secondelectrode 123 is a transparent conductive material. The first electrode121 and the second electrode 123 may be connected to a control circuit(not shown). The first electrode 121 and the second electrode 123 of thelight diffusion layer 120 may receive a DC voltage or an AC voltage. Thecontrol voltage V1 controls the light diffusion layer 120 to present thetransparent or non-transparent state.

For example, the control voltage V1 includes a control voltage V1 a anda control voltage V1 b, wherein the control voltage V1 a is transmittedto the first electrode 121 and the control voltage V1 b is transmittedto the second electrode 123. When the control voltage V1 exceeds thethreshold voltage Vt1, that is, when a potential difference between thecontrol voltage V1 a and the control voltage V1 b exceeds the thresholdvoltage Vt1, the polymer dispersed liquid crystal 122 of the lightdiffusion layer 120 presents the transparent state. Therefore, the lightfrom the light guide plate 130 passes through the light diffusion layer120 and reaches the display layer 110 in a transmissive manner (whichbarely affects a traveling direction of the light). When the controlvoltage V1 is lower than the threshold voltage Vt1, that is, when thepotential difference between the control voltage V1 a and the controlvoltage V1 b is lower than the threshold voltage Vt1, the polymerdispersed liquid crystal 122 of the light diffusion layer 120 presentsthe non-transparent state (e.g., hazy). Therefore, the light from thelight guide plate 130 passes through the light diffusion layer 120 andreaches the display layer 110 in a scattered manner.

FIG. 2A is a schematic cross-sectional view of a display panel 200according to another embodiment of the invention. The display panel 200includes a display layer 110, a light diffusion layer 120, a light guideplate 130, a back light source 140, a light reflection layer 215, and aone-way mirror layer 225. Details of the display layer 110, the lightdiffusion layer 120, the light guide plate 130, and the back lightsource 140 in the embodiment shown in FIG. 2A may be found in thedescriptions of FIG. 1A and FIG. 1B, and thus are not repeatedhereinafter. The light reflection layer 215 is disposed under the lightguide plate 130, and the light guide plate 130 is disposed between thedisplay layer 110 and the light reflection layer 215. The one-way mirrorlayer 225 is disposed under the light reflection layer 215, and thelight reflection layer 215 is disposed between the display layer 110 andthe one-way mirror layer 225.

A material of the light reflection layer 215 may be polymer dispersedliquid crystal. The light reflection layer 215 is controlled by at leasta second control voltage V2, so as to dynamically change thetransparency of the light reflection layer 215. When the control voltageV2 exceeds a threshold voltage Vt2, the light reflection layer 215presents a transparent state. When the control voltage V2 is lower thanthe threshold voltage Vt2, the light reflection layer 215 presents anon-transparent state (e.g., hazy). The threshold voltage Vt2 isdetermined by a material property of the light reflection layer 215.

A thickness of the light reflection layer 215 may be greater than athickness of the light diffusion layer 120. In this embodiment, thethickness of the light diffusion layer 120 may be 75 μm to 200 μm, andthe thickness of the light reflection layer 215 may be 201 μm to 1000μm. It is known from the result of an experiment that, in the case ofapplying no voltage, polymer dispersed liquid crystal that is 75 μm inthickness has better “visibility” (the farthest distance at which theuser sees the object through the polymer dispersed liquid crystal) thanpolymer dispersed liquid crystal that is 200 μm in thickness. Thethicker polymer dispersed liquid crystal reflects light better in thenon-transparent state. Therefore, the polymer dispersed liquid crystalof the light reflection layer 215 may serve as a white (or lightcolor/bright color) light reflection layer. When the control voltage V2is lower than the threshold voltage Vt2, the polymer dispersed liquidcrystal of the light reflection layer 215 presents the non-transparentstate, so as to reflect the light of the light guide plate 130 back tothe light guide plate 130. When the light diffusion layer 120 and thelight reflection layer 215 both present the transparent state, the useris able to see the object behind the display panel 200 through thedisplay panel 200 as well as see the image displayed by the displaylayer 110.

The one-way mirror layer 225 allows an external light 11 (not the lightof the back light source 140) to reach the light reflection layer 215through the one-way mirror layer 225, but reflects a light 141 from thelight reflection layer 215 back to the light reflection layer 215. Whenthe light diffusion layer 120 and the light reflection layer 215 bothpresent the transparent state, based on the one-way light transmissionproperty of the one-way mirror layer 225, the external light 11 passesthrough the one-way mirror layer 225, the light reflection layer 215,the light guide plate 130, the light diffusion layer 120, and thedisplay layer 110. Therefore, the user is able to see the object behindthe display panel 200 through the display panel 200. The one-way mirrorlayer 225 reflects the light of the back light source 140 to the displaylayer 110 and the light guide plate 130 guides the light of the backlight source 140 to the display layer 110, so as to improve thebrightness of the image of the display layer 110. When the lightdiffusion layer 120 and the light reflection layer 215 present thenon-transparent state, the light reflection layer 215 and the one-waymirror layer 225 reflect the light of the back light source 140 to thelight diffusion layer 120 and the display layer 110, so as to improvethe brightness of the image of the display layer 110. When the lightdiffusion layer 120 and the light reflection layer 215 present thetransparent or non-transparent state, a back surface of the displaypanel 200 presents a mirror state. The one-way mirror layer 225 mayprovide the display panel 200 an anti-peeping function, so as to preventthe image of the display layer 110 from being seen from the back surfaceof the display panel 200.

In some embodiments, according to the design requirements, the one-waymirror layer 225 shown in FIG. 2A may be omitted.

FIG. 2B is a schematic cross-sectional view of the light reflectionlayer 215 shown in FIG. 2A according to another embodiment of theinvention. The light reflection layer 215 shown in FIG. 2B includes afirst electrode 2151, a polymer dispersed liquid crystal (PDLC) 2152,and a second electrode 2153. The polymer dispersed liquid crystal 2152may relatively change/present different transparencies according todifferent electric field intensities. The polymer dispersed liquidcrystal 2152 is disposed between the first electrode 2151 and the secondelectrode 2153. A material of the first electrode 2151 and the secondelectrode 2153 is a transparent conductive material. The first electrode2151 and the second electrode 2153 may be connected to a control circuit(not shown). The first electrode 2151 and the second electrode 2153 ofthe light reflection layer 215 may receive a DC voltage or an ACvoltage. The control voltage V2 controls the light reflection layer 215to present the transparent or non-transparent state.

For example, the control voltage V2 includes a control voltage V2 a anda control voltage V2 b, wherein the control voltage V2 a is transmittedto the first electrode 2151 and the control voltage V2 b is transmittedto the second electrode 2153. When the control voltage V2 is lower thanthe threshold voltage Vt2, that is, when a potential difference betweenthe control voltage V2 a and the control voltage V2 b is lower than thethreshold voltage Vt2, the polymer dispersed liquid crystal 2152 of thelight reflection layer 215 presents the non-transparent state (e.g.,hazy). When the control voltage V2 is higher than the threshold voltageVt2, that is, when the potential difference between the control voltageV2 a and the control voltage V2 b is higher than the threshold voltageVt2, the polymer dispersed liquid crystal 2152 of the light reflectionlayer 215 presents the transparent state. The user may put his/her handbehind the display panel 200 to achieve human-machine interaction with athree-dimensional image of the display panel 200.

FIG. 3A is a schematic cross-sectional view of a display panel 300according to yet another embodiment of the invention. The display panel300 includes a display layer 110, a light guide plate 130, a back lightsource 140, a one-way mirror layer 225, a light reflection layer 315,and a light diffusion layer 320. Details of the display layer 110, thelight guide plate 130, the back light source 140, and the one-way mirrorlayer 225 shown in FIG. 3A may be found in the descriptions of FIG. 1Aand FIG. 2A, and thus are not repeated hereinafter. The light reflectionlayer 315 and the light diffusion layer 320 shown in FIG. 3A may bederived from the descriptions of the light reflection layer 215 and thelight diffusion layer 120 shown in FIG. 1A, FIG. 1B, FIG. 2A, and FIG.2B.

In the embodiment shown in FIG. 3A, the light diffusion layer 320includes a first region 1R and a second region 2R, and the lightreflection layer 315 includes a first region 1R and a second region 2R.The first region 1R of the light diffusion layer 320 and the firstregion 1R of the light reflection layer 315 are disposed opposite toeach other. For example, in a vertical projection, the first region 1Rof the light diffusion layer 320 and the first region 1R of the lightreflection layer 315 are located at the same position. The second region2R of the light diffusion layer 320 and the second region 2R of thelight reflection layer 315 are disposed opposite to each other. Forexample, in the vertical projection, the second region 2R of the lightdiffusion layer 320 and the second region 2R of the light reflectionlayer 315 are located at the same position. Moreover, a change of atransparency of the first region 1R of the light reflection layer 315may be independent of a change of a transparency of the second region 2Rof the light reflection layer 315. A change of a transparency of thefirst region 1R of the light diffusion layer 320 may be independent of achange of a transparency of the second region 2R of the light diffusionlayer 320. An example is described hereinafter.

In an embodiment, under control of the control voltage V1 and thecontrol voltage V2, the first region 1R of the light diffusion layer 320and the first region 1R of the light reflection layer 315 both presentthe non-transparent state, and the second region 2R of the lightdiffusion layer 320 and the second region 2R of the light reflectionlayer 315 both present the transparent state. In this embodiment, thelight reflection layer 315 and the light diffusion layer 320 are dividedinto a plurality of regions that are independently operable to beapplied to a human-machine interaction mode.

FIG. 3B is a schematic view of an image displayed by the display panel300 of FIG. 3A. In this embodiment, the second region 2R has a largerarea than the first region 1R. Under control of the control voltage V1and the control voltage V2, the first region 1R of the light diffusionlayer 320 and the first region 1R of the light reflection layer 315 bothpresent the non-transparent state, and the second region 2R of the lightdiffusion layer 320 and the second region 2R of the light reflectionlayer 315 both present the transparent state. For example, in the imageas shown in FIG. 3B, the display layer 110 may display a plurality ofthree-dimensional toy models in the second region 2R, and the system mayprovide a human-machine interaction interface behind the display panel300 for the user to see two hands behind the display panel 300 throughthe second region 2R and rotate the three-dimensional toy models 360degrees in the second region 2R, or disassemble or assemble the toymodels, so as to simulate the feeling of actually touching the toymodels. The display layer 110 may display the prices or current stock ofthe toy models in the first region 1R to provide the user more productinformation.

FIG. 4 is a schematic cross-sectional view of a display panel 400according to yet another embodiment of the invention. The display panel400 includes a display layer 110, a light diffusion layer 120, a lightguide plate 130, a back light source 140, a light reflection layer 415,and a one-way mirror layer 425. Details of the display layer 110, thelight diffusion layer 120, the light guide plate 130, and the back lightsource 140 shown in FIG. 4 may be found in the descriptions of FIG. 1Aand FIG. 1B, and thus are not repeated hereinafter. In this embodiment,the one-way mirror layer 425 is disposed under the light guide plate130. The light guide plate 130 is disposed between the display layer 110and the one-way mirror layer 425. The one-way mirror layer 425 allows anexternal light (not the light of the back light source 140) to reach thelight guide plate 130 through the one-way mirror layer 425, but theone-way mirror layer 425 reflects the light of/from the light guideplate 120 back to the light guide plate 120. The one-way mirror layer425 enhances the back light utilization of the display panel 400.

The light reflection layer 415 is disposed under the one-way mirrorlayer 425, such that the one-way mirror layer 425 is located between thelight guide plate 130 and the light reflection layer 415. A material ofthe light reflection layer 415 includes a polymer dispersed liquidcrystal. The light reflection layer 415 is controlled by the secondcontrol voltage V2, so as to dynamically change the transparency of thelight reflection layer 415. When the control voltage V2 of the lightreflection layer 415 is higher than the threshold voltage Vt2, the lightreflection layer 415 presents the transparent state. When the controlvoltage V2 of the light reflection layer 415 is lower than the thresholdvoltage Vt2, the light reflection layer 415 presents the non-transparentstate. Details of the light reflection layer 415 shown in FIG. 4 may befound in the descriptions regarding the light reflection layer 215 shownin FIG. 2A and FIG. 2B, and thus are not repeated hereinafter. When thelight diffusion layer 120 and the light reflection layer 415 present thetransparent state, the user is able to see the object behind the displaypanel 400 through the display panel 400 as well as see the imagedisplayed by the display layer 110. In some embodiments, according tothe design requirements, the light reflection layer 415 shown in FIG. 4may be omitted.

FIG. 5A is a schematic layout diagram of sub-pixels of the display layer110 and light guide microstructures 535 of the light guide plate 130according to an embodiment of the invention. FIG. 5B is a schematiclayout diagram of the light guide microstructures 535 of the light guideplate 130 according to an embodiment of the invention. FIG. 5C is aschematic cross-sectional view of the light guide microstructures 535 ofthe light guide plate 130 according to an embodiment of the invention.FIG. 5D is a schematic cross-sectional view of the light guidemicrostructures 535 of the light guide plate 130 according to anotherembodiment of the invention. Referring to FIG. 5A, FIG. 5B, FIG. 5C,and/or FIG. 5D, the light guide plate 130 includes a plurality of lightguide microstructures 535, wherein the light guide microstructures 535may be implemented on the light guide plate 130 by printing, carving,laser engraving, or stamping, but this embodiment is not limitedthereto. A geometric shape of the light guide microstructure 535 is thesame as (or similar to) a geometric shape of a sub-pixel 1143 (or pixel)of the display layer 110. In this embodiment, the geometric shape of thelight guide microstructure 535 is rectangular. In the verticalprojection, a position of any of the light guide microstructures 535corresponds to a position of the sub-pixel 1143 (or pixel) of thedisplay layer 110. Moreover, a width of each of the light guidemicrostructures 535 is an integer multiple of a width of the sub-pixel1143 (or pixel), and a length of each of the light guide microstructures535 is an integer multiple of a length of the sub-pixel 1143 (or pixel).Therefore, in the vertical projection, a boundary of the light guidemicrostructure 535 may not overlap the sub-pixel 1143 (or pixel).Because the boundary of the light guide microstructure 535 does notoverlap the sub-pixel 1143 (or pixel), the user does not easily see thelight guide microstructures 535.

In comparison, FIG. 6A is a schematic layout diagram of light guidemicrostructures 610 of another light guide plate 600. Similar to thelight guide plate 130 shown in FIG. 5A, FIG. 5B, FIG. 5C, and/or FIG.5D, the light guide plate 600 shown in FIG. 6A also includes a pluralityof light guide microstructures 610. A difference between the light guideplate 600 and the light guide plate 130 is that a geometric shape of thelight guide plate 600 shown in FIG. 6A is different from the geometricshape of the sub-pixel 1143 (or pixel) of the display layer 110.

FIG. 6B is a schematic layout diagram of the sub-pixels 1143 of thedisplay layer 110 and the light guide microstructures 610 of the lightguide plate 600 shown in FIG. 6A according to another embodiment. In theembodiment shown in FIG. 6B, the geometric shape of the sub-pixel 1143(or pixel) is rectangular while the geometric shape of the light guidemicrostructure 610 is circular. When the display layer 110 overlaps thelight guide plate 600, in the vertical projection, a boundary of thelight guide microstructure 610 overlaps the sub-pixel 1143 (or pixel).Because the boundary of the light guide microstructure 610 overlaps thesub-pixel 1143 (or pixel), the user will see the boundary of the lightguide microstructures 610.

To conclude, the display panel disclosed in the embodiments of theinvention includes the diffusion layer 120. The control voltage V1 maycontrol/adjust the transparency of the diffusion layer 120. In someembodiments, the display panel further includes the diffusion layer 120and the light reflection layer 215 that have different thicknesses forincreasing the back light utilization of the display panel. In someother embodiments, the diffusion layer 320 and the light reflectionlayer 315 are further divided into different regions that areindependently operable.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the disclosed embodimentswithout departing from the scope or spirit of the invention. In view ofthe foregoing, it is intended that the invention covers modificationsand variations provided that they fall within the scope of the followingclaims and their equivalents.

What is claimed is:
 1. A display panel, comprising: a display layerdisplaying an image; a light guide plate disposed under the displaylayer and guiding a light of a back light source to the display layer; alight diffusion layer disposed between the display layer and the lightguide plate, wherein the light diffusion layer is controlled by at leasta control voltage to dynamically change a transparency of the lightdiffusion layer, and a light reflection layer disposed under the lightguide plate such that the light guide plate is located between thedisplay layer and the light reflection layer, wherein the lightreflection layer is controlled by at least a second control voltage todynamically change a transparency of the light reflection layer, and athickness of the light reflection layer is greater than a thickness ofthe light diffusion layer.
 2. The display panel according to claim 1,wherein the light diffusion layer presents a transparent state when thecontrol voltage exceeds a threshold voltage, and the light diffusionlayer presents a non-transparent state when the control voltage is lowerthan the threshold voltage.
 3. The display panel according to claim 1,wherein a material of the light guide plate is a transparent material,and a material of the light diffusion layer comprises a polymerdispersed liquid crystal.
 4. The display panel according to claim 1,wherein the light reflection layer presents a transparent state when thesecond control voltage exceeds a threshold voltage, and the lightreflection layer presents a non-transparent state when the secondcontrol voltage is lower than the threshold voltage.
 5. The displaypanel according to claim 1, wherein the thickness of the light diffusionlayer is 75 μm to 200 μm, and the thickness of the light reflectionlayer is 201 μm to 1000 μm.
 6. The display panel according to claim 1,further comprising: a one-way mirror layer disposed under the lightreflection layer such that the light reflection layer is located betweenthe display layer and the one-way mirror layer, wherein the one-waymirror layer allows an external light to reach the light reflectionlayer through the one-way mirror layer, and the one-way mirror layerreflects a light from the light reflection layer.
 7. The display panelaccording to claim 1, wherein a material of the light reflection layercomprises a polymer dispersed liquid crystal.
 8. The display panelaccording to claim 1, wherein the light diffusion layer has a firstregion and a second region, the light reflection layer has a firstregion and a second region, the first region of the light diffusionlayer and the first region of the light reflection layer are disposedopposite to each other, the second region of the light diffusion layerand the second region of the light reflection layer are disposedopposite to each other, a change of a transparency of the first regionof the light reflection layer is independent of a change of atransparency of the second region of the light reflection layer, and achange of a transparency of the first region of the light diffusionlayer is independent of a change of a transparency of the second regionof the light diffusion layer.
 9. The display panel according to claim 1,further comprising: a one-way mirror layer disposed under the lightguide plate such that the light guide plate is located between thedisplay layer and the one-way mirror layer, wherein the one-way mirrorlayer allows an external light to reach the light guide plate throughthe one-way mirror layer, and the one-way mirror layer reflects thelight from the light guide plate.
 10. The display panel according toclaim 9, the light reflection layer is disposed under the one-way mirrorlayer such that the one-way mirror layer is located between the lightguide plate and the light reflection layer.
 11. The display panelaccording to claim 1, wherein the light guide plate comprises aplurality of light guide microstructures, and a geometric shape of anyof the light guide microstructures is the same as a geometric shape of apixel or a sub-pixel of the display layer.
 12. The display panelaccording to claim 11, wherein the geometric shape of any of the lightguide microstructures is rectangular.
 13. The display panel according toclaim 11, wherein a position of any of the light guide microstructurescorresponds to a position of the pixel or the sub-pixel of the displaylayer.
 14. The display panel according to claim 11, wherein a width ofany of the light guide microstructures is an integer multiple of a widthof the pixel or the sub-pixel, and a length of any of the light guidemicrostructures is an integer multiple of a length of the pixel or thesub-pixel.